Random finite element analysis on uplift bearing capacity and failure mechanisms of square plate anchors in spatially variable clay

Square plate anchors are increasingly used to provide uplift bearing capacity for both onshore and offshore infrastructures. Past research on the behavior of plate anchors mostly assumed that the soil strength is uniform or linearly increasing with depth without considering the geological uncertainty due to soil spatial variability. This study therefore conducted a series of three-dimensional random finite element analyses on the uplift bearing capacity and failure mechanisms of square plate anchors considering the combined effects of anchor buried depth and soil spatial variability. It was found that two typical types of failure mechanisms, namely, a localized rotational scoop failure mechanism and a global shear failure mechanism would form in random soils with relatively weak and strong soil strengths, respectively. A larger buried depth of at least 3B (B = width of plate anchor) is required to ensure a localized failure mode in random soils. Moreover, the mean uplift bearing capacity in random soils is generally lower than the corresponding deterministic value. For this reason, the deterministic uplift bearing capacity is generally overestimated. Finally, this study provided a quantitative approach to predict the probability of failure for plate anchors considering the combined effects of anchor buried depth and soil spatial variability, which may benefit the estimation of the probability of failure for square plate anchors as part of the conventional factor of safety design approach.